Modern commercial passenger aircraft utilize auxiliary airfoils which are extended from the leading and trailing edges of the aircraft wing to increase lift during takeoff and landing of the aircraft. Such auxiliary airfoils are known in the industry as "flaps", that usually extend from the trailing edge of the wing, and "slats" which extend from the leading edge of the wing. When extended from the wing, these auxiliary airfoils increase the size and the effective curvature or camber of the wing and also increase the effective chord of the wing over which the airflow passes to create lift. Accordingly, aircraft lift is increased when slats and/or flaps are extended from the wing leading or trailing edges.
Such auxiliary airfoils are segmented, and each segment is individually positioned by separate but coordinated drive mechanisms in order to maintain the desired configuration for the wing during extension of the auxiliary airfoils. Accordingly, it is desired to monitor the position and alignment of individual slat segments with respect to the other slat segments at all times during use of the auxiliary airfoils. For example, if a significant misalignment or skewing of one or more of the slat segments occurs, this may indicate that an undesired or unsafe condition exists, in which case the drive mechanism should be automatically shut down to prevent further misalignment or skewing of the auxiliary airfoil system.
A problem in designing such a system is that there will always be normal relatively small spurious movements caused by the wing structural deflections, dynamics of the aircraft, or temperature changes that could confuse such a detection system, and cause it to respond to minor misalignments that do not present problems for the aircraft.
U.S. Pat. No. 3,935,754 relates to the detection and indication of the failure or loss of the primary drive train of a flap actuator system having both primary and secondary drive trains. An alarm signal is transmitted when the secondary drive train takes over. It is not intended to detect differences in the position of individual flap segments on a single side of the wing.
U.S. Pat. No. 4,181,276 relates to a system for monitoring synchronized motion of slats on the part and starboard wings. The system does not monitor differences of positions between flap segments on the same wing.
Another prior art detection and actuation system known to applicants uses a grounded extension spring attached to a monitoring cable and a hook attached to a micro switch. The hook is positioned to attach to the extension spring when it extends a predetermined amount in response to increased load in the monitoring cable. The hook will then actuate a microswitch which provides a signal indicating a misaligned condition.
Accordingly, it is an objective of this invention to provide improved apparatus to detect a serious displacement, or misalignment, of one or more adjacent auxiliary airfoil segments during their extension or retraction, while ignoring smaller spurious deflections that cannot be avoided and do not cause problems in the extension or retraction of the airfoil segments.